Þorbjörn on the brink

/ 05/11/2023

The stunning photograph of Thorbjörn Volcano was honestly stolen under fair usage for educational purposes, all rights remain with the Photographer.

Volcanoes rarely follow human timescale and human planning. This time it is Þorbjörn that decided to ruin things just after Albert had published a truly nice read about Santa Maria.

Þorbjörn better do as told below, otherwise Albert will have words with the volcano in question for ruining his article scheduling.

 

Background

Longterm GPS-trend data, Image by the Icelandic Met Office.

In the last 4 years the Reykjanes Fires have kept us amused, and as Þorbjörn is getting closer and closer to erupting I thought we should begin with a short recap.

Before Fagradalsfjall erupted 3 times it all began with Þorbjörn suffering from a powerful earthquake swarm, and an intense inflationary period where it uplifted 80mm.

The magmatic intrusion stopped that time at around the 5km mark, and since then the magma has been sitting there in situ, waiting for better times, and instead we got the 3 Fagradalsfjall eruptions as the pre-show amusement.

The first of those was a pretty tourist eruption that continued for quite some time, the second one threatened to overrun the road, a couple of houses, and burial site. Thankfully none of this happened.

And the third one was fairly unremarkable as Icelandic eruptions go, but the tourists that got there in time got their money’s worth at least.

 

Last few weeks

Earthquake map-plot, image from the Icelandic Met Office.

During the last couple of weeks Earthquake activity resumed over at Þorbjörn, and that in turn developed into a proper earthquake swarm with magma-tectonic earthquakes. But, to muddle the waters a swarm also started toward the tip of the Reykjanes peninsula, but those earthquakes steadfastly remained tectonic in nature.

About a week ago rapid inflation set in as the intruding magma pushed up the area above, and this inflation can be seen well across the entire Reykjanes Peninsula. By now the inflation has reached 60mm, plus the 80mm that was intruded in the last seismic crisis, so in total the area has inflated 140mm.

The GPS gives this as 100mm in total, but that is due to subsidence caused by Fagradal, and due to the area naturally subsiding over time. But the area directly above the magma is 140mm higher than what is should have been compared to other non-affected areas, if you catch my rift (drift).

 

Earthquakes

Happy little “bendy” low-frequency earthquakes, image by the Icelandic Met Office.

If we track the earthquakes that are larger than 2.5Mw we end up with them peaking at about 2.1km, those that are smaller are not well defined enough to be able to pinpoint depth enough to really be trustworthy, so let’s stick with the 2.5Mw as a good marker for what is a minimally trustworthy earthquake (no earthquakes are ever trustworthy…), and only if it has a 99 percent marker and is corrected by hand.

2.1km is at, or very near the border of where a volcano will become a runaway train in regards of erupting, due to buoyancy the magma will continue upwards if left alone, and 400 meters higher and it will start to nucleate out volatiles, and at that point nothing can stop an eruption from happening.

Regardless of this, the earthquake swarm is continuing due to magma building up the pressure, so it is not even left alone to its own devices.

 

Contractions

 

 

 

Breyting plots by the Icelandic Met Office.

At 00.04 Sunday morning the mountain suffered from a sudden strain increase at the same time as there was an earthquake doublet.

If it had been a drunkard outside a pub, this was the first dry heave before that type of eruption. And if we would state it with another physical human process, Þorbjörn had a contraction but the birthing canal was not dilated enough.

During that time there was a tremor episode also indicating that it was one of those “close, but no fish” situations.

But when contractions have started there will be a baby in the end. Yes, it may be a false contraction, and the baby will shoot out a few days later, but it is sort of assured that soon you will need a mountain of diapers at hand.

Now it depends on how fast the earthquakes breaks open the volcanic birthing canal, I do not think it will take a long time.

 

Eruption time?

Happy little tremors recorded in Grindavik, image by the Icelandic Met Office.

I would say that it is pretty close, at anything from a few hours, up to a couple of weeks. The Icelandic Met Office has it as within a year, but that statement came prior to the last 24 hours.

I would definitely take a bit of time to go out and grab some popcorn and find some nice webcams of Grindavik.

 

Eruption spot?

Volcanoes that have a fissure line like Þorbjörn are tricky to say where they will erupt specifically, but a good guess would be 3-5km from the town centre of Grindavik towards the Þorbjörn mountain itself.

This is a tricky spot since magma pouring out there relatively quickly would get to the town. There is also the potential that the dyke will propagate further south near the surface and pop up in someone’s basement.

I seriously hope that the last thing will not happen since it would be dangerous.

 

Conclusion

Þorbjörn is close to erupting now, and if it happens it will most likely impact the lives of the citizens of Grindavik. I do know that they are well informed and are ready to go within minutes of notice, and if it pops up at around where the earthquakes are heading, there will be time to evacuate.

I am not sure if the Icelandic authorities will try to save Grindavik by digging trenches and spray water on the advancing magma front like they did under Fagradal 2 and the Heimaey eruption respectively, but I would sort of assume that the Icelanders will have a go at it since they tend to fight their volcanoes.

CARL REHNBERG

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766 thoughts on “Þorbjörn on the brink”

  1. Road 43 has already received temporary repairs but will remain closed until further by decisions of the police.
    It is estimated that half the population of Grindavík has already left.

    • I was so pleased when I heard some where moving out. Not a good scenario.
      IMO seem convinced lava will not resch Grindavik. I hope they are correct but do not share their faith.

    • Here’s hoping the dike will continue the run for the sea while everyone at Grindavik gets out of there.

      • Magma plus water is a very explosive combination. The impact could be felt beyond the Reykjanes Peninsula. Planning to fly anywhere for Christmas?

        • I’d rather not witness another Heimaey or Leilani even if that means some folk will not be able to cross the pond for Crimbo.

    • Earthquakes today with a depth of less than 2km.

      Source: https://skjalftalisa.vedur.is/#/page/map

      From memory, shallow quakes at Fagradlalsfjall at the end of the dike were triggered quakes rather than magmatic during 2021 and 2022. The eruption sites, themselves, was relatively aseismic beforehand.

      I don’t know whether there is an aseismic zone here.

  3. The dike may well pop up east of the power plant, but it could quite easily extend along the previous fissures as far as Grindavik (or even the sea). So for them to say Grindavik should be safe based on scientific guesswork is quite risky.

    There appears to have been some quakes activated on the Krysuvik, Brenninsteinfjoll and Reykjanes systems today also, perhaps set off in response to what’s happening at Svartsengi. Unless they just haven’t been accurately located.

    • There was a swarm in 2012 on Brenninsteinfjoll, I wonder if it was accumulating magma deep down back then?

  4. WOW! 4.5 at 1km depth is getting closer quickly. If this is confirmed and I see no reason why not.

    Friday
    10.11.2023 21:51:18 63.904 -22.501 1.8 km 4.5 90.03 7.8 km NNW of Grindavík

  5. Well the dike goes right under Grindavik… Quite a lot has changed in the 10 hours I left it alone.

    I know there is no absolute confirmation but this can really only be a dike with the sort of signal. It is entirely possible this doesnt erupt but now there is a rift open it is alnost inevitable in the near future.

    To be honest, if just the bottom of the dike is at 5 km, the top is way above that already. Fagradalsfjall managed to erupt with much slower supply from a greater depth 3 out of 4 times including the first breakout, it isnt looking good. Krafla has a huge rift zone to absorb large intrusions, Svartsengi and Reykjanes appear not to, the rifts going maybe 20 km and that is to the north which this dike didnt do.

    • How big could this eruption be in volume terms Chad, Carl, Hector, Albert, Thomas?

      • going by the uplift of 7cms I would say it could be humungous.
        Now one of the supermen you have called on will use more technichal terms. But big beyond doubt.

          • I would suggest Holuhraun will be a closer match than Litli-Hrutur. the latter was a bit of a damp squib, this one is more likely to be a rocket. Time will tell.

          • Not a chance of a Holuhraun-size eruption; where’s the magma chamber? Where’s Bárðarbunga?

            Statements like that are alarmist and unhelpful, IMHO.

          • Mike is correct, there just no magma reservoirs around, and Holuhraun probably had 3 different feeds, we are lucky it turned out so small in the end.

            I am quite certain that and Hunga-Tonga will be the eruptions of my lifetime, but for different reasons.

          • I meant in terms of length not volume Mike. It is entirely possible it floods across the land rapidly as it has done in the past, covering 12km in a thin layer. The fissure system its on extends almost to the north coast and almost certainly into the sea in the south.

          • That is not what previous flows in this region have done. They stay confined and cover a few square kilometer, I am not expecting a long-lasting eruption.

          • sorry. i didnt mean it would be Holohruan scale but way larger than Litli Hrutur. Didn’t mean to alarm anyone and surely I didnt just that Litli hrutur would be small in comparison.

          • I was just going off the previous eruptions. 1210-1240AD eruption is about 15km long. Whether it was one eruption across several fissures or multiple from similar locations over 30 years it makes little difference.

            Chances are it will be small, but there’s been a larger than usual influx and it’s taking a hell of a lot of pressure to breach the surface. Hence I think it will be bigger than Fagra.

          • It appears I am the only one that understood what you were saying about the scale of the eruption Andy but perversely others chose to take our lighthearted word wrongly. Hey Ho. such is life,

      • There’s a bit of information to keep in mind. Mid-ocean ridges are dominantly intrusive. Ocean crust is mostly built from brief dikes and slowly crystallized gabbros in deep magma or mush bodies, with a bit of lava on top. It’s true that Iceland it’s not your typical mid-ocean ridge and does have a superior lava output, the oceanic crust under Bardarbunga IS 8 times thicker than usual oceanic crust after all, but still, magma goes into dikes and that is often its final destination. We already have a big event, a 12-km long dike, and maybe that will make the eventual eruption small or non-existent. If there is a lot of space to fill underground it can take up most or all of the magma. If more dikes intrude the same swarm, which tends to happen (Fagradalsfjall, Krafla Fires, or Manda Hararo in Afar), the dikes will overflow more and the eruptions will get more substantial over time. I think maybe 0.2 km3 would be among the biggest you can get here without a shield. However, the eruptions here are quite intense and that’s the danger. It is not the same if Fagradalsfjall erupts 0.1 km3 in a few months, than if Svartsengi (Sundhnukur and Eldvörp) erupt 0.1 km3 in a matter of hours or days.

    • Looking at history it will not be as big as Holuhraun thankfully.
      But 0.1-0.5 is possible.
      And the area of the sill and uplift would put it in the lower ballpark of that, but it is obviously depending on how much influx there will be, and how longlived it will be.
      Starting volume is though relatively low at 0.1ish.

    • History is your best guide here; look at the volumes erupted in previous cycles of activity in this area.

      And the short answer this reveals is ‘pretty small’; this agrees with the inferred volume of the intrusion so far – but then again, there’s no such thing as a ‘small’ eruption if it’s under your sofa!

      • I was just cracking a joke about it.
        2 seconds after they have finished that protective wall around the powerplant it will burst up through the floor inside the plant.

        Yeah, I think you and me are the party poopers on this one.
        Small, and time will decide the final tally.
        If it goes for a few years it could by all means create a small shield theoretically, but I would say around Fagra II.

    • The size is not possible to know because we dont knkw how much magma us involved. Just because we saw this sill form recently doesnt mean all of the other ones formed in the last few years arent available or even if there are many more deeper down. I remember that before the eruption on La Palma in 2021 it was said there was 13 million m3 of magma in the intrusion and the volume kf the eruption when it ended was about 0.25 km3, and with a very similar magma pathway complex to what probably exists under Reykjanes (actually, a lot deeper, coming straight fom over 40 km).

      Not that this will happen now but the eruption could be sizable. My estimate is between 30 million and 100 million m3, but remember if this is high intensity the volume is almost irrelevant, the upper number is larger than any of the individual eruptions of the Krafla Fires and a few of those sent lava flowing 5,6 even as much as 8 km away within days on flat ground…

      • Not sure where this idea of 0.1-0.5 km3 being ‘small’ comes from. 1 km3 eruptions in Iceland are not typical, they stand out because of size and impact but are rare. Holuhraun was the 5th biggest lava flow in the past 1000 years in Iceland. And most of the multiple tens of km3 eruptions are also shields, which are not formed fast.

        Same thing as not considering a VEI 4 big, they only happen once a year or less on average, to me that is uncommon and noteworthy. I consider any explosive eruption over 0.1 km3 to be significant and 0.2 to be large. Any effusive eruption over 0.1 km3 is large, even if you can get stuff that is much larger.

        In that context, the expected eruption here is probably going to erupt lava at a rate comparable to a VEI 4 eruption, happening under or very close to a town…

          • The last eruption before Holuhraun to get over 1 km3 was Laki, and the one before that being hekla in 1766 and Katla in 1755, although that last one would have fallen far short if it was effusive, tephra is more voluminous than lava rock. But counting that still eruptions that big are not that common, just that the small eruptions are missed due to staying subglacial or being way up in the highlands that has only really been well observed for a few decades with any certainty, although doubtless people had been seeing things on occasion throughout history.

            Laki was also very abnormally large, it was the 3rd largest Holocene eruption known from Iceland, the second being Eldgja and the largest Thjosahraun. Shields are not considered in this but are not really comparable. Its not even known for certain they are actually completely monogenetic, some might be but others might have erupted at intervals separated by years over a few centuries.

        • I guess it depends what you compare it to. If you compare it to Piton de la Fournaise, Etna, or Stromboli, 0.1-0.2 km3 is absolutely massive. If you compare it to Mauna Loa or maybe some of the “stronger” Galapagos volcanoes it’s normal-sized. In Iceland of course you have shields and fissure eruptions that go over 10 km3 and up to 50 km3 so it might not stand out much. In Mexico you have shield volcanoes, which are probably monogenetic, with 10-20 km3. And Yellowstone has rhyolite lava flows that surpass 100 km3. So it really is a matter of perspective.

      • Most Icelands eruptions are fast Aa flows and yes go to around 0,1 km3 per eruption at least from the central volcanoes, thats what been the case with most of the pre fagradalshraun flows, and indeed 0,1 km3 is mindblowingly huge for a human thats the volume that takes to fill most of the 2018 pit in Kilauea.. when I was smaller I also tought that 0,1 km3 100 million cubic meters are small but most other volcanoes does far smaller lava flows, even the summers 13 million cubic meters flow was mindblowingly huge when I saw drones and other footage of it. Grimsvötn avarge VEI 3 s so are rather small events but fast

        • Fagradalshraun was also 0,1 km3 and gave some idea how insanely huge that volume is in human perspectives!

  6. “Kattholt issued a statement that in the event residents of Grindavík and surrounding areas need to evacuate their homes due to an imminent volcanic eruption, Kattholt has decided to open an emergency shelter for those cats in need. Cats will be accepted on Saturday, November 11, and Sunday, November 12, between 9-11 a.m. Additionally, they’ll be accepted during opening hours on weekdays from 9 a.m. to 3 p.m.”

  7. Jon Frímann writes in his blog that IMO confirmed that magma is rising. However, he also states

    “This does not seems to be connected to Svartsengi magma (Reykjanes volcano) dyke intrusion. How much magma and what volcano it is connected is unclear at the writing of this article.”

    That statement is a bit weird… I am convinced that the current events are clearly linked to previous intrusions and the sill which recently formed.

  8. The earthquake swarm keeps moving towards the SW and is now in the ocean. Is there any chance we end up with a submarine eruption (which would be disappointing for us but great news for Grindavik)?

    • Unlikely, I think. It is heading for an eruption in-land. But an eruption off the coast could actually cause a bigger explosion and cause more problems than you might expect.

    • The length of this dike could result in eruptions on labd and in the ocean. And, as a result, through Grindavik…

      Eldvörp goes into the ocean, and so do the Stampar fissures right at the tip of the peninsula, and possibly some of the fissures from Krysuvik on the south coast although the latter of those would be buried by lava so only speculative.

    • I’m absolutely speechless… Monumental moment for Iceland…

      • Didn’t see the comments above, didn’t mean to double post!

    • Not before time in my view. Now at least evacuees can get some help.

      • The problem in my view is that the longer these large quakes continue the more the infrastructure breaks down. Better to get people out now before the roads start to break up.
        I had a nephew in an earthquake zone and when shops start to shut because of damage from quakes then life rapidly becomes difficult.

    • Although several of us posted about the evacuation at more or less the same time, I’d like to point out that I was the only one to misspell the name Grindavík. So that’s gotta count for something. 🙄

  13. I think that by now any itinerant Grindavikians that swung by know that they are to evacuate after reading the above.
    I do not mind over-stating that an evacuation is ordered.
    It is after all sort of important.

  14. Has anything surfaced? Drums and tremor don’t show any activity yet.

    • No, but my guess is that they evacuate in the unlikely case the eruption starts really close from the town… or in someone’s basement. Maybe they are also worried about stronger earthquakes that might break the roads? All speculation from my part, but it’s better to be safe than sorry.

      • indeed. Once roads start to break and shops are forced to shut normal life is hard to sustain.

        • Also I hadn’t realized, but it looks like some buildings are damaged. The nursing home had to be evacuated earlier.

    • I actually saw that happen on the fagradalsfjall cam. It wasnt so much a cliff fall as one rockfall. not at all unexpected in such large quakes.

      • I am fairly sure it happened during the 5.2 quake but cannot remember the time for sure.
        I did check the quakes after and saw the recent 5.2.

  17. Utterly incredible how many 3s there have been in such a short space of time.

  18. From RUV
    Height, or depth, of magma tunnel unclear

    Víðir cannot say how high the magma tunnel has reached, but events have moved quickly in the last few hours.

    It would be good if people could leave Grindavík in the next two to three hours, he says.

    Response teams and key employees in the town will remain.

  19. I was just thinking it might be wise to evacuate…

    I read the bulletins from the uptick in activity before Holuhraun just earlier tonight and a) this level of eq/tremor activity was not seen that fast over the period before the eruption b) the activity decreased in the day/hours before it erupted and c) when the rift started it propagted fairly fast.

    Even considering ghostquakes it is almost as there has been a 5G-highway of magma opened into Reykjanes.

    As this really sped up around 5 PM today and we now see a pattern of a many km long dyke 6 hours later it is better to be proactive than not. It was not really that many hours from a “normal” day with 5-600 eq’s on the 28.08.2014 untill Holuhraun erupted. Not saying this is similar in size or development, but the pattern in similar development is there. Timescale different.

    If we consider the fairly long period with +5 km (depth) in activity at Reykjanes and how little timespan we have instrumental data from historical – to know how fast this has developed in the past – from the area I for one will sleep better tonight knowing they decided to do this. They want people out during the next 2-3 hours so it is not an emergency evacuation. 🙂

    Many new updates here in the last few minutes btw;

    https://www.ruv.is/english/2023-11-10-civil-defence-level-of-danger-live-396249

    • Now this DID surprise me.

      Workers leave power plant

      Contractors have been asked to leave the area at the Svartsengi power plant until Civil Defence have a clearer picture.

      The plant can be remotely controlled.

      Is there something they have noticed that isn’t being told yet?

      • Actually been told. There is a dyke forming along Sundhnjúkagígar. Not only has there been crazy earthquake activity all day, but the GPS stations are also showing clear evidence of a dyke forming fast so they are not taking any chances.

      • Here is what RUV says:
        The signs of magma movement include significant subsidence in the Sundhnúkur craters, indicating that the magma might be shallow below the surface.

        The southern end of the crater row is about 1 km from the nearest buildings in Grindavík and approximately 1500 meters from the Svartsengi power plant.

        The Icelandic Meteorological Office notes a substantial change in seismic activity, moving south towards the town of Grindavík. According to the Icelandic Meteorological Office, there is a likelihood that magma movement has extended beneath the town of Grindavík.

        The volume of magma involved is considerably larger than seen in the major magma intrusions related to the eruptions at Fagradalsfjall.

    • seeing the contractors had only just arrived to start the defensive wall it would suggest to me things might be moving more quickly that IMO had expected.

          • Thanks and now i’m asking, “So all the white glowy stuff isn’t lava, right?

          • Thankfully not lava. That is steam that is always present but apparently the plant is being operated remotely now.

          • not seen any cars moving so I think they must have evacuated earlier.

      • That bit also surprised me. Could mean that action towards Svartsengi is expected so soon that any work there is pointless and dangerous OR it could mean that Svartsengi is no longer the primary concern and that all those earthwork contractors need to be on call for a very different task near or in Grindavík.

        • It means that the dyke that seems to be forming is approximately 1.5 kilometers from Svartsengi so for security reasons it has been evacuated. You don’t outrun a volcano, so better safe than sorry.

  21. It cannot be ruled out that the magma tunnel goes under Grindavík

    Hector had it first! well done Hector.

  23. https://www.mbl.is/frettir/innlent/2023/11/10/mun_meiri_kvika_en_adur_hefur_sest_a_svaedinu/

    Google translation of the official notice : “ The amount of magma involved is significantly greater than what has been seen in the largest magma intrusions that occurred in connection with the volcanic eruptions at Fagradalsfjall.”

    So if significantly greater than Fagradalsfjall 1.0 in 2021 then we are talking about significantly more than 150 million cubic metres. It’s incredibly interesting that our understanding of this intrusion size and its origin (which system etc) has been upended in just a few hours.

  25. Right now the southern tip of the dyke has passed by Grindavik and entered the ocean.
    Do not that the length of the dyke does not necessarily equate where it will pop up.
    The dyke at Fagra I rand 1km further than the eruption point.

    That being said, the dyke is now extending into the sea to the South, and propagation North seems to have stalled for now with main earthquake activity is out in the ocean near Grindavik.

    If an oceanic eruption would happen it is not the end of the world, it would though impact flights depending on wind direction.
    If that happens expect roosters to form as the lava is close to breaching the surface, but prior to that it would probably just be turbulent water, water discolouration, and as it closes the surface we would start seeing water fountaining prior to the roosters.
    If it continues for long enough the eruption would quickly turn purely magmatic as an Island or landspit form.

    I am a succer for volcanic island formations, so I will keep my fingers crossed for that.
    Anyway, if it erupts at sea Grindavik would become ashy, but remain safe, unless of course new vents form North of the initial wents like Fagradal II & III did compared to Fagra I eruptions site (and to each other).

    Serial dyke eruptions tend to always happen further in towards the bottom feeder, so from an oceanic eruption it is likely that the next breakout point would be towards the landside or inside Grindavik.

    We shall see..

  26. Just read this on IMO.
    The amount of magma involved is significantly more than what was observed in the largest magma intrusions associated with the eruptions at Fagradalsfjall.

    So in my opinion it is totally likely this eruption, should it decide to show, WILL be far larger than the fagradalsfjall eruptions, And no that is NOT being alarmist.

    • And thats realistic too with Svartsengi fast and brutal, the volume of the comming eruption is highly debatable But yes probaly will be larger than this summer eruption

    • I agree, it is likely to become larger.
      But still not on the scale that Iceland can do in other places, but pretty large for Reykjanes on average.

  27. Definitely a Graben forming over the dyke now.
    Station GRIC has jumped a lot:
    North 14cm
    East 18.5cm
    Down 15cm

    ?fbclid=IwAR0jyjZ86u5acDFRDX8CbD3X4BzFJHcbEiCeDOsEDcwkWLLYYkIxN8PSaWg

    • We might get a small little Surtsey outside of the port, and that would annoy the fishermen no end.

      • I love submarine eruptions that break surface and become Islands. Can it happen twice in my lifetime? I doubt I could be so lucky. I am of course talking about Icelandic eruptions as Iwo Jima already did it again.

        • Surtsey was sadly 8 years before my time.
          So, it would be my first Icelandic island formation, but fifth in my lifetime that I have witnessed.

          • Ah you would have so loved Surtsey. We only had black and white TV in those days but I watched every news bulletin enthralled by the sight.
            I have followed it history ever since and so glad it still exists.

          • For me the first Icelandic eruption I remember was Krafla Fires.
            I remember sitting riveted infront of the TV watching it.

        • It happens a lot more often than you think 🙂 just that most islands are eroded away. But even in the past decade there is Nishinoshima, and before it blew up Hunga Tonga Hunga Ha’apai was also looking to be pretty permanent had it not done what it did, the ocean wasnt going to wash it away any time soon anyway.

          Islands formign are common, what is rare is that they stay around for more than a few months.

          I do not think an eruption from the current crisis is going to stay so small as to just make a tiny island in Grindavik harbor though.

          • Hunga Tonga was older than me…
            The most common spot for them to form is though out in the red sea.

          • I meant the cone it formed in 2014, which was most of the island that blew up in 2022. Its rare for eruptions that make islands to not have some tiny islands as neighbors.

          • It depend upon if it would have vents propagating backwards over time IF it erupts near the harbour.
            But, it would be fairly small for island, Reykjanes is not the best spot for big stuff.

            I expect double flow rates at peak of Fagra II and an eruption lasting a few months, but that is about it.
            There is though the famous Orange Swan, and we get a flowrate after a while of 2-8 cubic metres per second lasting a century and we get Grindabunga as a shield is born.

          • Surtsey was the odd one out since it erupted so far away from Heimaey.

          • An eruption lasting a few months is just what the doctor ordered for me. Every year I suffer from winter depression. Having something to carry me through to the new year would be wonderful. Once the days start to get lighter so does my mood. This past month in England has been dreaful with rain and floods. Our local supermarket has been closed because of flooding for 3 weeks now. Not fun. So I have a lot of sympathy for residents of Grindavik. To be displaced at this time of year is bad, to maybe not have hot water and electricity if the geothermal plant goes under would be dreadful.

          • Not to forget Iwo Jima just this month. Already 20 meters high

  28. Latest RUV.is update:

    “The magma tunnel lies under Grindavík – “A very big event”

    The meeting between the scientists of the meteorological office and representatives of the civil defense ended just before four o’clock. There, data was reviewed that show that a magma corridor now runs under Grindavíkur town.

    Based on the data, a decision was made to call all responders from Grindavík.

    The corridor runs from Sundhnjúkagígir and from there to the southwest through Grindavíkurbær and onward. The size, length and volume of the magma tunnel is not known. It is difficult to say exactly how deep the magma is, but the earthquakes that have been recorded in the last hours in the area originate at a depth of two to three kilometers.

    A natural disaster expert at the Icelandic Meteorological Office says it is clear that this is a very large event.”

    • So the base of the dike is at 2-3 km, the top is shallower than that then… Its not certain but with how fast this dike was formed its unlikely the eruption is going to be far off.

  29. My thoughts are with the citizens of Grindavik and affected area. It is always so traumatic to have to leave one’s home. Watching with interest and remembering the warnings from Carl about this area so many years ago when Volcano Cafe was first erupting. He said clearly to “Watch this Space” I may not post often but still watch and read with interest. The world should watch the way Icelanders deal with emergencies. Orgainised , with great Authority and the people seem to have more common sense then those elsewhere. They follow advice of the experts and pull together for the common good. I realise the population is small and are used to natural events but the panic, looting and other assorted idiocracies seen in other emergency areas is not seen.

    • Hello Diana. Great to see you post once again. I remember thosevery early days of volcano cafe too. I used to post a lot then but lost my account after yahoo got hacked and I could no longer access my email account. Good to hear from you again. I am getting old and cannot even remember the nameI posted under then.

  30. Good morning!
    Seems that the earth doesnt have we…already to work

  32. Here is a photo you might find interesting, Grindavík and in the foreground, the old craters named Sundhnjúkagígar.

    • How far is it for a down-crawling lava to reach Grindavik?

      This is from “Assessing the impact of lava flows during the 2020 unrest of the Svartsengi…” [Tarquini et.al.2020].

  33. Morning. Has anyone heard anything about borehole/well water temperatures? With magma so close to the surface it would seem surprising if there was no impact. I guess the power station would not be publicising any data.

  34. We have to be within hours of an eruption at this point

    • I could still be days away. Right now the earthquake activity is still high, meaning that a lot of rock cracking is going on at depth. Once the earthquake activity drops, there are 2 possibilities: either the intrusion stops, or the magma is close to the surface meaning an eruption will occur. The latter possibility is most likely, but it may take some more time.

  35. The dike grew more overnight, it is some 17-18 km long now! The last time I plotted the earthquakes it was 12 km long. Most remarkably the dike tip is 2 km into the ocean south of Grindavik as Randall, Swiiscompos, Carl, Cabrageo, and maybe others have been pointing out. Blue translucent balls are earthquakes of the dike swarm (since around 17:30 UTC yesterday). Red lines are the postglacial fissure systems of the area, from left to right: Stampar, Eldvörp, Arnarsetur, and Sundhnúkur.

    I’m not sure if it will erupt or not, the first dike in a sequence often encounters strong extensional strain, so there’s basically a lot of space to fill underground and that may keep it from overflowing. It might still eupt though, and could do so anywhere along that 18 km long area.

    Something really interesting is that the dike seems to follow the Sundhnúkur fissures very well. I had some suspicions that fissure systems in the Reykjanes Peninsula are polygenetic. Mostly because Trölladyngja and Krýsuvík seem to be formed by many overlapping subglacial fissures that built 2 long ridges. I think the present reactivation of Sundhnúkur confirms that the fissure systems are polygenetic and active across multiple Reykjanes cycles. So it is likely we will see more of this fissure system, and also that Eldvörp, Arnarsetur, and Stampar could reactivate at some point. It is interesting and still unclear to me what is the role of the sill/sill complex under Thorbjörn in all of this, presumably it is feeding this dike, or helping at least, but its extent would likely connect Sundhnúkur and Eldvörp, maybe even Stampar too.

    • Thanks very much for this chart. Makes things clear and also shows the bigger picture.
      Much appriciated

      • Seconded!
        Excellent contributions by Héctor over the past few days, greatly appreciated.

    • Sounds like the Krafla fires a bit, same stuff large dykes and fissure eruptions and yes they are polygenetic being basicaly hidden central volcanoes, and once its stops cutting horizontaly it will probaly go towards the surface like it did the previous times having a Mauna Loa caldera like eruption close to a town or inside it is not good in anyway the eruption rates coud be 100 s to 1000 s of cubic meters a second so good they have evacuated the town

  37. The order of the color pens on the Grindavic tremor chart remain inverted compared to their relative steady state before the large quake clusters of 12 hrs ago. From the top, that order was purple-green-blue and now it is blue-green-purple with everything elevated a bit. Again, other than the colors being associated with labeled Hz ranges I’m clueless as to what this representation means technically — BUT I feel safe in thinking it means something significant changed with that big quake storm and hasn’t changed back as of 0930 or so Grindavic time.

    • The tremor plots show the amplitudes of the shaking measured by a seismometer. It works like this. During a certain time interval (I’m not sure how long, something like 1-5 minutes) the maximum amplitude is recorded. Then for each 15 minutes, it plots the value for the two intervals that have the highest and lowest maximum amplitude).

      If all is quiet, a single quake will be contained in one interval. The plot will then output a vertical line, where the bottom remains at baseline level and the top is the amplitude of the quake.

      If there is wind noise from a storm, all intervals will measure somewhat higher values, so the baseline is raised.

      When there is an intense earthquake swarm like now, all intervals will xontain quakes and measure large amplitudes, so the plot is raised a lot. There will still be different amplitudes in different intervals, so the line gets thick.

      Finally, when there is eruptive tremor, the amplitude is constantly high. Each interval will measure a high value, so both the top of the line and the bottom will be high. You get raised levels like now, but the line is thinner.

      Then we have special cases like the fountaining episodes in 2021, where each 15-minute point contained both intervals of fountains with high amplitudes, and periods of silence between the fountains. Then the plot got super thick.

      The different colors represent data that has been filtered to contain different frequency ranges. Apart from the differences I mentioned above, different sources contain different proportions of frequencies, so the colors give an extra hint of what the source might be. Personally, I ignore the colors. The general behaviour as I explained above give the best information anyway.

  38. Was just watching the litli hrutur webcam out of interest and some puffs of steam caught my eye. Steam seems normal as it’s web, but puffs suggest that the earth is breathing.

    As I watched about half way up the slope on the left the puffs seemed to get more and appear across a straight line across the scarp. I don’t think it’s my imagination.

    I guess the earthquakes could have opened some cracks at Fagradalsfjall and hot gases are leaking out.

    Thought it might be interesting to keep an eye on.

    Of course as I typed the most came down and it’s hard to see anything!

    • My thinking is the earthquakes are possibly disturbing accumulated ground water and/or the still very hot material erupted during the summer and allowing them to come into contact triggering geyser like activity. Basically a notch or two down from a pheratic event.

  41. At this point some InSAR pictures would be good. In the last three eruptions it has been possible to pinpoint the upcoming eruption site within a 200m radius just by looking at the butterfly pattern of the InSAR measurement.

    Even though there was a lot of dyke propagation in all three episodes, the final eruption spot ended up pretty much where the maximum initial deformation was observed.

    The deformation this time is huge. 120cm (yes, cm) separation has been measured between two stations on opposite sides of the dyke.

        • With a drop of about a meter in Grindavik, would that be visible on the shoreline? The Fagradalsfjall camera is a bit wet at the moment and it would probably need a Timelapse to really see it. But wouldn’t a meter rise in sea level (or rather drop in the land) in a port be visible? Like at that market in Campi Flegri?

          Not that there is anyone in Grindavik to look at it this morning (I hope).

      • Thanks! I wrote my comment below before I saw this. I’d say somewhere between the crater row and Grindavík looks like the most likely eruption site.

        • You’re welcome Tomas. That area you mentioned is also my most likely site at present, maybe a bit more concentrated between Hagafell and Grindavik, but certainly extends SW and NE of that area (as per your dyke figure).

          • Yes, I drew my picture guess based on GPS movements and beach balls, before the dyke started to form. Had I drawn it today, I think we would be in perfect agreement.

      • Notice that the entire Reykjanes fault has slipped, almost to the very end of the peninsula. The “wing” lobes of the butterfly pattern are also shifted accordingly.

        This already looks like the entire deformation of the 2021 runup, if not larger.

    • The Grindavík GPS is the one with the maximum subsidence. It has dropped a whopping 100cm, so it’s right inside the graben. Thorbjörn has dropped 90cm, but is a bit off to the side, so there is a possibility that the maximum deformation is at Sundhnúkagigur.

      To summarize, the available data at the moment does not look good for Grindavík.

    • With 120 cm of change, couldn’t interferometry be used on visible light data instead of C/X band radar? I remember someone playing with that a few years back but now I’ve forgotten where I read about it. I guess I have to assume the results weren’t satisfactory.

      • My bad. It was seeing if they could calibrate the latest generation of $1000 grade consumer drones to establish monthly captures of a grid, using visible light, of course. The nav units have (evidently) improved to where holding a specified altitude above a specified set of coordinates borders on possible. None of this is applicable to Grindavic. Feel free to cull these posts as they are far off topic, with my apologies.

        • Not interferometry. I use visible/IR interferometry, and it is used for very small changes, of microns, not meters. You could get it from direct comparison of images – that will work albeit not from public satellite images which have resolutions of meters, not centimeters. Radar interferometry is still the best for centimeter changes over large areas

  44. Can someone explain the subsidence taking place? It seems counter intuitive?
    Thanks!

    • from the new post written by Albert:

      “Thorbjorn has sunk by 40 cm. This happened because the dike is forcing the rock apart. That the sinking is so much indicates the magma has shallowed. “

    • Basically the dike is forcing the rock on either side of it out to the left and right. This means the rock directly above is being stretched thinner and so it drops.

  45. Hey there just wanted to give you a quick heads up and let you know a
    few of the pictures aren’t loading correctly. I’m not sure why but I think its a
    linking issue. I’ve tried it in two different browsers and both show
    the same outcome.

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